Recent philosophical and psychological researches show that memory, not only stores information but also process it. It's possible one to have a meta-representational memory despite the propositional content and attitude of the present meta-representation being different from the propositional content and attitude of the thought that the meta-representation is causally derived. So, the question is: if we take for granted that this kind of memory doesn't require content or attitude identity, what is the permissible range of aberration between the original content and the memory content? This paper proposes some conditions to define when a present meta-representation has the status of memory of a past thought, despite the difference of content or attitude. The condition for diachronic content similarity is the same proposed by Sven Bernerker. The attitude condition is a new one: the attitude that S thinks (at t2) himself having taken (at t1) towards p and the attitude that S took at t1 towards p* are sufficiently similar if and only if they are the same or the attitude of the present thought is entailed by the past attitude.